This is U2’s first indoor arena tour in a decade, which is why the band is doing two shows in each of the 19 cities it visits.

The tour follows the late 2014 release of U2’s “Songs Of Innocence,” which was pre-released as a free download by Apple to iPhone users. And while that seemed a nice gesture, it raised some ire among fellow musicians who complained it “devalued” their music. Some iPhone users also were irked that the album was automatically downloaded into their iTunes library.

When all was said and done, Apple estimated that over half a billion iTunes Music Store customers worldwide received the free album. To date, “Songs of Innocence” has been streamed 81 million times and has been downloaded by 30 million fans, according to concert promoter Live Nation.

The band takes the stage at 7:30 p.m. Friday and Saturday. Tickets are $40 to $140.